Interpretive Summary: Diets for rainbow trout have historically contained high quantities of fish products. Research has found alternatives to these fish products but at the cost of reducing fish growth. The USDA-ARS Trout-Grains Project, officially titled “The integration of nutritional, genetic and physiological approaches to improve production efficiency of rainbow trout (Oncorhynchus mykiss)” was initiated with a primary goal to identify cost effective replacements for fish products in aquaculture diets. The project team consists of two fish nutritionists, a fish geneticist, a grain chemist and a plant geneticist. This group of scientists addresses a range of issues, including selection/development of alternative plant material with improved nutritional profiles, development of methods to economize the use of grains, and development of families of trout that are better able to utilize nutrients from plant-based feeds. The nutrition component of the project focuses on evaluation of new and traditional ingredients, nutrient requirements for specific life stages, and identification of nutrients in fish meal not present in plant meals.

Technical Abstract:
Feeds for rainbow trout have historically contained high quantities of fish meal and fish oil as cost effective sources of both essential amino acids and fatty acids. Research results from around the world have identified ingredieints to replace fish meal and fish oils, but limits still exist in completely reomoving these ingredients from the diet. The USDA-ARS Trout-Grains Project, officially titled “The integration of nutritional, genetic and physiological approaches to improve production efficiency of rainbow trout (Oncorhynchus mykiss)” was initiated with a primary goal to identify cost effective replacements for fish meal. Scientists for this group address a range of issues, including selection/development of cereal grains with improved nutritional profiles, development of methods to fractionate valuable components of grains, and development of families of trout that are better able to utilize nutrients from plant-based feeds. The nutrition component of the project focuses on evaluation of new and traditional ingredients, nutrient requirements for specific life stages, and identification of nutrients in fish meal not present in plant meals. Finally we are developing a database of nutrient availability from plant-based ingredients that will have potential to supply the nutritional needs for rainbow trout in aquaculture. Highlights from this research have been: 1) Taurine may be conditionally indispensable when only plant-derived protein sources are utilized. 2) Vitamin premix formulations benefit from modification when fish meal is replaced by plant derived indredients, or when poor quality fish meals are used in extruded trout feeds. 3) Starch amylase/amylopectin rations in energy feed ingredients will affect carbohydrate and energy digestibility.